Antenna coupling and tuning system for communication or broadcast receivers



Feb. 9, 1943. c. w. WANDREY 2,310,720

ANTENNA COUPLING AND TUNING SYSTEM FOR COMMUNICA'IION OR BROADCAST RECEIVERS Filed April 21, 1941 8 Sheets-Sheet l E 5 co 1 a a?) L; (0

INVENTOR QAIPE/VCE With/mew BYM] ATTORNEY Feb. 9, 1943.

w. WANDREY 2,310,720

C. ANTENNA COUPLING AND TUNING SYSTEM FOR COMMUNICATION OR BROADCAST RECEIVERS Filed April 21, 1941 8 Sheets-Sheet 2 8 I INVENTOR QARf/YCE 14/ Wan may AT ORNEY Feb. 9, 1943.

c. w. WANDREY 2,310,720 ANTENNA COUPLING AND TUNING SYSTEM FOR COMMUNICATION OR BROADCAST RECEIVERS Filed April 21, 1941 8 Sheets-Sheet 3 A ORNEY 1943. c. w. WANDREY 2,310,720

ANTENNA COUPLING AND TUNING SYSTEM FOR COMMUNICATION OR BROADCAST RECEIVERS Filed April 21, 1941 8 Sheets-Sheet 5 Q P E E emu T% .N. R w m NNWWT I. A 2 MY CB Feb. 9, 1943. c .w. WANDREY ANTENNA COUPLING AND TUNING SYSTEM FOR COMMUNICATION OR BROADCAST RECEIVERS Filed April 21. 1941 8 Sheets-Sheet 6 N E NTCR Cz/mwcz W WANG/8'5) ATTOR EY Feb. 9, 1943. c. w. WANDREY 2,3 0 2 ANTENNA COUPLING AND TUNING SYSTEM FOR COMMUNICATION OR BROADCAST RECEIVERS Filed April 21, 1941 8 Sheets-Sheet 7 m I92 I79 H JHIHH W306. I 307 "Mgr INVENTOR F'l G CLAAfA/CEM haw/My ml, la 5 AT RNfi Y Feb. 9, 1943. c. w. WANDREY 2,310,720

ANTENNA COUPLING AND TUNING SYSTEM FOR COMMUNICATION OR BROADCAST RECEIVERS Filed April 21, 1941 8 Sheets-Sheet 8 RECEIVER RNEY Patented Feb. 9, 1943 ANTENNA COUPLING AND TUNING SYSTEM FOR COMMUNICATION OR BROADCAST RECEIVERS Clarence W. Wandrey, Chicago, Ill., assignor to Zenith Radio Corporation, a corporation of Illinois Application April 21, 1941, Serial N 0. 389,650

48 Claims.

v The present invention relates to control systems and apparatus and more especially to improvements in circuit adjusting apparatus for radio receivers. This application is a continuation in part of the application of Clarence W. Wandrey and James W. Sharp, Serial No. 359,124 filed September 30, 1940, for Antenna coupling and tuning system for communication or broadcast receivers.

It is a general object of the present invention to provide novel control apparatus of general use in a wide variety of electrical equipment, in-

cluding laboratory apparatus, power generation apparatus and motive power equipment, and also tunable apparatus such as radio transmitters and receivers.

Another object of the present invention is to provide novel control systems for adjustable circuits.

Another object of the present invention is to provide novel control means for the circuit changing elements of adjustable electrical circuits.

Another object of the present invention is to provide tuning apparatus especially adapted for use in compact radio equipment such as marine, aircraft and automobile radio equipment.

A further object of the present invention is to provide for operation, in a novel manner, of the tunable elements of a radio receiver.

A still further object of the present invention is to provide novel means for tuning a radio receiver to any one of a plurality of predetermined signal sources.

A still further object 01' the present invention is to enable ready and convenient adjustment of any one of a plurality of selectable tuning positions at will.

A still further object of the present invention s to provide novel tuning apparatus in the manufacture of which accurate machine work to close tolerance is not required, and wherein loose fitting parts and play between the parts or either will not affect accuracy of tuning.

It is a further general object of the present invention, in one aspect thereof, to provide novel antenna tuning and high frequency energy transfer circuits, and in another aspect, to provide novel control systems for tunable circuits.

In coupling a radio receiver to an antenna circuit having very low capacity, it is difficult to obtain maximum transfer of signal energy. Also, it is difficult with an antenna of this type to obtain a signal for use in the receiver which is free from interference and locally produced noise.

In dealing with a small low capacity antenna or very high impedance, such as a simple insulated short rod, difficulties are encountered in obtaining efiicient transfer of energy. Antenna coupling circuits of the prior art are only imperfectly adapted to couple antennae oi the type just mentioned to the input circuits of a radio receiver and these known coupling circuits have inherent defects which cannot be avoided in practice. They have limited range or frequency spectrum coverage in use, and can transfer only a small portion of a desired frequency or wave length band. Wide variations in coupling are experienced as the adjustable circuits which they employ are adjusted or tuned to select a desired signal source. From a practical standpoint, these previously known antenna coupling arrangements cannot be effectively used especially where space is a factor as in a broadcast receiver for installation in aircraft, or a vehicle such as an automobile, since these known tuners do not lend themselves to compactness of design, flexibility or ease of control. Apparatus embodying circuits available prior to this invention could not be designed for ease and cheapness of manufacture, thereby to conserve materials, reduce the cost of material and eliminate unnecessary and costly manufacturing operations. Practical control equipment of suitable design for ordinary or special purposes could not be used eifectively with these prior art coupling circuits. connection, as stated above, the present invention aims to provide novel tuning apparatus of general use in a wide variety of tunable equipment, and this novel apparatus is especially suited for use in the field of compact radio apparatus such as aircraft and automobile radiore ceivers employing high impedance low capacity antennae.

Accordingly, one of the major objects of the present invention is to provide improved signal energy transfer from an antenna to the input circuit of a radio or broadcast receiver.

Another important object of the present invention is to overcome the difficulties mentioned above, and other difficulties which are inherently present in prior art adjustable circuits and controls for the adjustable elements of these circuits.

Still another object of the invention is to pro- .vide novel circuits, adjustable for tuning, which will permit the maximum transfer of signalling energy from a carrier receiving device, such as an antenna, to a translating device such as, for

In this,

example, an amplifier in a radio receiver or other repeating device. 7

A still further object of the invention is to provide novel tunable circuits which will reduce interference caused by undesired oscillations from sources external to the receiver.

A still further object of the invention is to provide a novel antenna coupling circuit in a superheterodyne radio receiver, permitting use of a lower intermediate frequency while at the same time providing separationbetween the desired frequency and any interfering frequency.

A still further object of this invention is to provide a novel form of coupling between the amplifying portions of a radio receiver and an antenna of high impedance, which coupling will provide uniform sensitivity throughout a desired tuning range.

The manner of realizing the foregoing objects and obtaining the general and special advantages discussed above and, also, other and more specific objects of the invention will become apparent as the following detailed I description proceeds with reference to the accompanying drawings which:

Figure l is a diagrammatic showing of electrical and mechanical features of the present invention embodied in a radio receiver, certain parts of which are shown in a conventional manner.

Figure 2 is a fragmentary detail of the apparatus of Figure 1 drawn to an enlarged scale and illustrating another position of the parts.

Figures 3 and 4 are additional fragmentary details drawn to an enlarged scale.

Figure 5 is a diagrammatic representation of the antenna tuning and coupling circuit of this invention in one form. v

Figure 6 is a plan view, partially in section on line 8- of Figure 7, of a radio receiver showing the invention in a modified form, certain parts of the receiver being omitted for the sake of cleamess of illustration.

Figure 7 is a vertical section taken on line 1-1 of Figure 6 as viewed in the direction of the arrows.

Figures 8 and 9 are fragmentary detail views of the modification of Figure 6. v I

Figure 10 is a view in front elevation of the receiver of Figure 6.

Figure 11 is a diagrammatic showing of the electrical connections of the tuning device of Figures 6 to 10.

Figure 12 is a diagrammatic showing of electrical and mechanical features of another modification of the tuner control of this invention.

Figure 13 illustrate a detail of the modiflcation of Figure 12.

Figure 14 is a view similar to Figure .6 illustrating a further modification of the invention taken on line 14-44 of Figure 15.

Figure 15 is a vertical section taken on line 15-45 of Figure 14.

Figures 16 and 17 are fragmentary detail views ceiver designed more especially for use in a vehicle. It i to be understood, however, that the invention is not so limited. Referring to Figure 1, reference character 5 indicates the various sections of the receiver which are more or less conventional. All of the circuits of the receiver are not shown but the circuits necessary for an understanding of this invention are shown externally of the diagrammatic representation 5. One of these externally shown circuits is the antenna 6 together with the associated antenna coupling and radio frequency tuning circuit indicated generally by the reference character 1, which includes tunable inductances 8 and 9 and a trimmer condenser 10. The portion 1 of the receiver, which cooperates in a novel manner with radio frequency amplifier I4 is an important feature of the present invention and will be explained more in detail hereinafter in connection with the description of Figure 5 illustrating an equivalent circuit for the antenna 6.

Reference character 16 indicates the oscillator frequency control circuit which is shown connected to the oscillator and mixer section of the set. This oscillator control circuit, which in actual practice forms arr-internal part of the oscillator and functions in the usual manner, comprises a tunable inductance l1 effectively connected in parallel with an inductance l8 which is inductively coupled to a tickler coil I9.

The combined station selecting device and station pre-setting device, indicated generally by reference character 2|, is an important feature of the invention and is illustrated in modified form in Figures 6 to 9. The fundamental features and principles of operation of the device 2| will now be explained with reference to the diagrammatic showing on Figures 1 to 4 of the drawings.

Tuning is accomplished by a plurality of longitudinally movable cores 23, preferably manufactured from ferrous materials. In the embodiment shown in Figure l, which illustrates the fundamental features of this aspect of the inwith other types of receivers the cores 23 will vary in number and location. The cores 2! are adjustably secured as at 28 to a yoke member 21 which forms a part of a movable carriage 28 comprising the above mentioned yoke member, a solenoid core 29 and a suitable connecting link such as the member II which joins the solenoid core to the yoke 21. Means, illustrated as the guide member 32 which is rigidly secured to a stationary portion of the receiver, serves to sup port and guide the carriage 28 for longitudinal movement. spring 33, surrounding the member 3| and reacting between one arm 34 of the guide 33 and a disc or other member 36 suitably secured to the connecting member 31', tends to move the carriage 28 to the left as viewed in Figure 1 and serves to maintain the yoke member 21 in a position determined by one of a, plurality of stops or abutments 31 or 31A, which contacts the member 38 (Figure 3) pivoted at 39 to the yoke 21. The member 38 is maintained in position to contact a stop 31 in selected position by spring 40. These springs permit the stops 31 to revolve about the axis of the shaft 44 without interference from Means, such as the compression.

vided with athreaded stem the member 38 permitting any position of the stops to be selected at will.

From the parts thus far described, it will be seen that as the carriage 23 is moved to the left, cores 23 will enter the inductances 8, 9 and I! and thereby progressively increase their inductance to effect tuning of the circuits with which these inductances are associated. When this progressive movement is arrested at any given point, the tunable circuits including these inductances will be tuned to a given frequency. The stops 31 serve to arrest movement ofthe carriage 28, there being as many positions of rest for the carriage as there are stops 31, and hence the tuned circuits will be in resonance for one frequency foreach stop thereby providing ready means for selecting, one at a time, a predetermined number of different frequencies. These frequencies may be those assigned to a plurality of broadcast stations thus affording convenient means for selecting a desired broadcast station.

The carriage 23 is moved longitudinally in a continuous manner to effect manual tuning, a desired stop 31 being positioned to arrest movement of the carriage; the several stops being arranged so that they may be individually adjusted or pre-set by mechanism operated from a handle or knob 4| and now to be described.

To the end that any desired stop 31 may be positioned to arrest movement of the carriage 28, these stops are carried by discs 42 and 43 which are secured upon and rotate with the shaft 44. In the embodiment shown, each stop 31 is pro- 41, which receives and s pports an internally threaded pinion 48. The s 'p 31A carries a pinion 43 which cooperates with a gear 5|, and which is preferably internally threaded with a higher pitch thread so that the stop 31A may be moved longitudinally at a higher speed by which manual tuning is effected in a manner later to be described. As a given pinion 48 or the pinion 43 is brought into the position occupied by the pinion 43 in Figure 1 of the drawings, the stop associated with the pinion will be moved longitudinally in a direction which depends upon the direction of rotation of the pinion.

The shaft 44 is mounted for rotation in suitable bearings which may be integral with or secured upon a mounting plate (not shown) and this plate may also carry the guide 32. A bevel jecting member gear 53 on the shaft 44 meshes with a similar gear 54 which is journaled in a stationary bearing member 56. A shaft 51, which has secured at its end the handle or knob 4| previously described, is slidably and rotatably journaled in suitabl bearings (not shown) and is keyed or splinecl in the bevel gear 54.

A third shaft 6| extends at right angles to the shaft 51 and lies in a plane at a different elevation from that of the knob shaft 51. This third shaft 6| is slidably and rotatably Journaled in suitable bearings (not shown) The shaft 6| is biased toward the right in Fig. 1 by a compression spring 8| and carries the previously mentioned gear 5| which is secured thereto. The gear 5| is adapted to mesh with a gear 62 secured to a shaft 63 and carries a tuning knob or hand wheel 44 which may-project through an aperture 66 in an escutcheon plate 61 or other casing member whereby it can be readily manipulated by hand.

From the description of the parts including the shafts GI and 63, it will be observed that shaft 51.

as the shaft 6| is shifted to the left as viewed on Figure 1, the gear 5| will mesh with gears 43 or 43 and the gear 62 whereby upon turning the knob 64, the stops 31 or the stop 37A, respectively, will be moved longitudinally. When the stop 31A occupies the position shown so as to move the carriage 28 and the tuning cores 23, rapid manual tuning of the receiver is provided throughout its entire range. The assembly, including the discs 42 and 43 carrying the stops 3'! and 31A, is rotated to place any of these stops in the position shown as occupied by stop 31A on Figure 1 of the drawings whereby to arrest movement of the yoke member 2'! by engagement with the member 38 projecting therefrom.

This rotation of the discs 42 and 43 is accomplished in the following manner: As the knob 4| is rotated, gears 53 and 54 turn the shaft 44. When the knob 4| is rotated to its extreme position in a counter-clockwise direction as viewed from the bottom of Figure 1, a radially pro- 12' (Figs. 1 and 2) engages the projection 13 on the shaft 6| moving the latter towards the left to bring gear 5| into meshing engagement with the gears 43 and 62 so that continuous and rapid manual tuning may be obtained as mentioned above. As hereafter explained, the carriage 28 is automatically withdrawn to the right in. Fig. l by the solenoid I9 and returned to the left by the spring 33 each time the knob 4| is rotated.

Pre-setting of the stops 3! so that desired stations may be selected at will is provided for in the following manner: A member 16 having a conical shaped cam 11 is secured to the shaft 51 and may be of unitary construction with the stop 12 if desired. When the shaft 51 is drawn outwardly by means of the knob or handle 4| the conical cam 11 engages the previously described member 13 to effect movement of the shaft 6| toward the left thereby engaging the gears 49, 5| and 62.

With the parts in this position any one of the stops 3! which is in the position occupied by the stop 31A in Fig. 1 may be adjusted by rotating the knob 64 to move the carriage 28 to and fro to position the cores 23 relative to the inductances 8, 9' and i! to tune in a desired station at that setting.

After a stop 31 has been adjusted to tune in a desired station the knob 4| may be pushed inwardly, rotated to any other desired position and pulled outwardly to effect adjustment for preselection of other stations. After the stops 3! have been set in this manner knob 4| may be pressed inwardly and as further described below the series of selected stations will be received as the knob is turned.

Energization of the solenoid 19 for the previously mentioned core 29 withdraws the carriage 23 toward the right as viewed in Figure i when the knob 4| is turned for any purpose such as to select a pre-set station, to select the manual tuning position for the stop 31A or to select any given stop 31 for adjustment to a new position.

To energize the solenoid 19 immediately upon turning the knob 4| a switch indicated diagrammatically at 8| and comprising a movable contact 32 is positioned so that the contact 82 is operated by a notched cam 83 rotatable with the A power source indicated at 84, which may if desired be the source supplying the several units of the radio receiver energizes the coil 19 immediately upon closure of the contacts of the switch 8| which causes the solenoid core 29 and' carriage 28 'to be withdrawn toward the I right. Energization by a locking circuit 86 and 81, the armature 88 which is position by link from including the relay contacts latter contact being carriedby anattracted to circuit closing the coil 19 when it is ener of the coil 19 is: maintained sitionto another without pausing at any intergized, Whenthe core 29 is at or adjacent its full limit of travel to the right, member 89 projecting stop 31 or 31A just selected by rotation of the In order to provide convenient means for in-* dicating' the frequency or station to which the radio is tuned a scale member 9I-is provided which has printed or otherwise reproduced thereon a suitable scale 92'graduated in kiloc'ycles or" other desired units. A pointer 93 is this scale and is driven by a suitable means such;

as the rodor strand 94 connectedto a projec tion 98 on the core 29 or any desired part of I the carriage 28. A lightspring 98 may be used if slidable on I desired to,assist in moving the pointer 93 in the 1 event thatthe member 94 is not suflicientlyrigid to accomplish this purpose.

Another portion of the scale may be provided if desired with movable clip'members 99'which may be employed to indicate the pre-set' positions on the scale. These indicators 99 are preferably in the form of clips as suggested above who movable along series of stations for at any time.

While the operation of the tuning control mechanism of Figure 1 will, it is believed, be obvious from the foregoing detailed description of the parts and their functions, the operation of the complete apparatus will bebrlefiy reviewed.

It will be assumed previously set to different longitudinal positions so that five different transmitting stations may be selected by turning the knob 4|, and that the preselection may be set up that the stops 31 have been the member 9| asa new 1 knob 4| is in the position illustrated so that the 1 stop 31A is in'contact the carriage affording manua tuning by the knob 84. When it is desired to listen to a prowiththe member 38 on grain from a station whichwill be tuned in by the next succeeding position of knob 4|, the knob is turned counter-clockwise one step. It will be understood that details of the mechanism may be readily arranged operable from the manual position in a clockwise direction. Immediately upon moving the knob from its manual position the circuit controlled by the switch 8| will be closed, whereuponthe solenoid 19 will be immediately energized to withdraw the carriage from the stop 31A to the so that the knob may beright permitting'free rotation of the assembly 42 and 43, so that the next to the position previcarrled by the discs successive'stop 31 will move ously occupied by the stop the solenoid 19 is maintained'until the core reaches its extreme limit of travel to the right, whereupon the relay contacts 86 and 81 are opened to interrupt the locking circuit which maintains energization of'the solenoid. At orv before this time the stop 31 will have come to rest in position for engagement by the member 38 on'the yoke 21 so that as the-carriage 28 re- 31A. Energization of 29 Y turns toward the left it will be engaged by the stop therebytuning the inductances 8, 9 and I1 and the circuits associated therewith to the station.

It will be apparent that continued rotation of knob 4| in a counter-clockwise direction will tune in flvepre-set' stations, one at a time, and that the knob 4| may be moved rapidly from one pomediate point. It will be seen that apparatus embodying the novel pre-settable tuning mechanism of this invention permits ready and accurate selection of a desired station with a complete'absence of shock or jar inthe parts. '10

When desired, as pointed out above, the entire frequency range of the receiver may be covered rapidly by the tuning knob 64 which corresponds to the usual tuning knob in the ordinary radio receiver.

idler gear 5| will be in mesh with the tuning knob gear 82 the stop 31 to be adjusted and the member 38..

When this is accomplished the knob 4| is drawn outwardly causing the conical cam 11 to shift the idler gear shaft 6| to the left against its biasing spring .6|. The tuning knob 64 is then coupled to the stop pinion so that upon rotation of the knob the stop may be moved in longitudinal direction until a desired station istuned in, whereupon the knob 4| may be pressedinwardly;

disconnecting the gear drive from the tuning a knob and preserving the new position of adjustment'for the stop. This operation may be performed for any one of thestops 31. This entirely novel method of pre-setting the means for selecting a desired station at will is, as pointed out above, an important feature of this aspect of the invention. a

The antenna coupling circuit 1 referred to above will now be described in greater detail with reference to Figures 1 and 5 of the drawings. As the elements shown in Figure 5 are present in Figure '1, the same reference characters will be used for both figures. Figure 1 is shown in Figure 5 as being equivalent to a signal source I04 and a capacity I06 in series, this combination of circuit elements being shunted by a capacity Ill. The rectangle 8 encloses this equivalent circuit. The capacity I0 of the equivalent antenna circuit just described. corresponds to the trimmer condenser I0 of Figadjustable so that the resonant frequency of the tunable circuit III may be adjusted within close limits when using acoil 9 which, by reason of manufacturing tolerances, departs from ,previously determined design characteristics,

Because of the high impedance signal source,

shown as the rod antenna in Figure 1, high in-' With-the parts in the position of Figure lot the drawings, the shaft BI carrying the and the pinion 49 on the stem ofstop 31A. "Turning of the-tuning dial 64 will member 38 on the yoke 21, the knob 4| The rod antenna 6 of 'A second tunable circuit III ductance is necessary for coils 8 and 8. And, for effective coverage of a sufficiently large frequency band, the coils 8 and 9 are preferably long and have a relatively small diameter. In this way the average coupling from one turn to another is low when the tuning cores 23 are withdrawn. Small wire for the coils and 8 is preferable to obtain suflicient turns in a given length of coil. This results in a low reactance to resistance ratio, which expression is termed the Q of the coil. This relatively low value of Q would, if occurring in known antenna tuning circuits, result in inferior discrimination or station selectivity. When employing coils of the type Just described having a value of Q, which may be lower than that of coils designed for capacitive tuned receivers, in'

the coupling and tuning circuits of the present invention, excellent selectivity and noise discrimination results. Also, material and assembly costs of the coils will be relatively lower as solid wire may be used for winding the coils and cheaper shielding may be used.

4 fulfill this condition of maximum transfer of signal energy, this transfer being efficiently obtained as circuits I08 and Hi can be resonated to the desired signal frequency, and the circuits are readily adjustable or may be adjusted initially to provide optimum coupling.

In this connection it is to be noted that the inductance of the related coils is simultaneously varied and applications for this may be found. in circuit details where it is desired to resonate two circuits to the same frequency, to frequencies which must be maintained in fixed ratio to each other or to frequencies which must be separated by a fixed amount. The frequencies may be varied over a wide range while maintaining a desired fixed relationship between them.

The common capacitative coupling provided by capacity I09 discriminates particularly against undesired high frequencies since the reactance decreases as the frequency increases and, therefore, the voltage appearing across the terminals The signal input voltage received from the antenna is transferred by the tunedcircuits l0t and II i and appears substantially undiminished in magnitude across the terminals of the capacity H2. This desired and useful signal voltage may be impressed between the anode and grid of a radio frequency amplifier, for example, amplifier H of Figure 1, or it may be-utilized in any manner known to the art. In practicing this invention, it has been found that a standardradio receiver equipped with. the antenna coupling circuit of this invention gave twice as good-a signal to noise ratio at 600 kc. as the same set with a high Q coil and a known coupling arrangement.

In the embodiment disclosed by Figure 1 of the drawings, the antenna coupling arrangement of the invention transfers signal energy to the previously mentioned radio frequency amplifier M which may be of conventional design. The output circuit of the amplifier I4 is untuned, the principal circuit element thereof being the resistor H4 which cooperates in the usual manner with the blocking and coupling condenser ill feeding the mixer grid. The resistor I l 4 together with the radio frequency choke N1, the inductance H0 and capacity I I0 provides means to pass a band of frequencies of desired width so that the radio apparatus may be tuned over this band with uniform response if desired, or with greater sensitivity for predetermined portions of the band. The condenser H9 is shown as being adjustable, but is set once to obtain maximum attenuation of signals having frequencies in the neighborhood of the intermediate frequency, 7

In the following description of the operation of the receiver of Figure 1, which embodies the novel antenna coupling circuit of Figure 5, the theory of signal energy transfer and discrimination against unwanted signals by means of coupled circuits as it applies to this aspect of the invention will be briefly reviewed. Discrimination in any antenna tuning circuit must be suilicient, for obvious reasons, to prevent strong undesired signals from being passed along to the amplifier or amplifiers and this is especially important in a super-heterodyne receiver where undesired signais reaching the converter grid can produce many spurious responses since the converter acts as a mixer. Cascade tuned circuits or R. F. tuned circuits will provide the necessary discrimination. However, efficient coupling must be provided between the cascaded circuits. The circuits described in connection with Figures 1 and of the condenser H2 decreases as the frequency increases. An additional advantage of the antenna coupling circuit provided by this invention also flows from this. Most disturbances, such as ignition noises from an internal combustion engine, are of high frequency, and two sections of a pi filter are provided by the circuit 1 of the invention to attenuate these disturbances which heretofore have been very troublesome. The first of these filter sections includes the inductance 8, the inherent capacity I06 of the antenna plus capacity I 0 and the capacity I09. The sec ond filter section comprises the condenser I08, the inductance 0 and the capacity H2. Because of the greatly improved selectivity, and in particular because of high attenuation of signals in the image range, it is possible to simplify and reduce the cost of circuit elements which follow, at the same time maintaining their efficiency. The antenna system described above permits commercially satisfactory image ratios to be secured when an untuned radio frequency stage, such as is provided at i H and its associated parts in Figure 1 described above, are employed.

Figures 6 to 10 of the drawings disclose a modified form of tuner control which provides a ready means for tuning a radio receiver of any kind by manipulation of controls located in any suitable or convenient position on the receiver or by means of a remote control device preferabb' of the type disclosed in the co-pending application of E. F. McDonald, Jr., Serial No. 347,516, filed July25, 1940, and bearing the title Radio control system. It will be understood, however, that any simple type of circuit controller or switch may be used to effect operation of the tuning device from a remote point, and that a plurality; of switches located at a number of conveniently accessible points may be employed. Each switch of the plurality of switches may serve to control the tuning mechanism independently of or in conjunction with one or more of the remaining switches.

The tuning control mechanism of Figures 6 to 10 indicated by reference character if includes features of the mechanism 2| of Figure l, and, therefore, the similarity existing between these embodiments of the invention will/be pointed out as the description proceeds. The receiver may be of any conventional type, such as is shown diagrammatically in Figure 1, but as illustrated by Figures 6, 7, and 10', the tuning device is designed for embodiment in a compact auto radio receiver I22, the general features of which are illustrated in Figures 6 and '7 of the. drawings. Figure 11 also indicates diagrammatically the position of the remote control device mentioned a above, which is positioned for actuation by the foot of the driver of the automobile.

The plurality of tunable inductances I24 (Fig. 6) corresponding in function to inductances 8, 8 and I1 of Figure 1, are tunable by plungers I26 of ferrous material, resiliently secured at I36 to a yoke member I21 which is slidably mounted on a reduced portion I28 of a solenoid core I29. The shoulder I3I provided at the end of the solenoid limits slidable movement of the yoke, I21 on the portion I28 against which it is moved by the thrust oi. a compression spring I32A which reacts against an abutment provided by the cap I33. The solenoid I30 slidably receives the core I28 and is provided at one end with a buffer member I32 of rubber or other resilient material which cushions the shdable yoke I21. A spring I34 serves to move the yoke I21 to the right as viewed in Figure 6 and also performs the function of maintaining the yoke member in a position determined by one of a plurality of stops or abutments I36, there being-six of these stops in the modification shown in Figures 6 to-lO. However, it will be understood that a greater or lesser the pawl I64 to step the ratchet wheel a distance of one tooth. Stop members I6I and I62 carried number of these stops may be provided depending upon the number of stations which are to be selected automatically.

Each of the stops I36 is provided with an internally threaded aperture in which is received, in threaded engagement, an externally threaded rod I 31.- These rods, sixin number, are rotatably carried by a pair of disc members I38 and I38 secured against the ends of an enlarged hexagonal portion I of a shaft I42. It will be understood that the enlargement I4I will have 1 Each rod I31 projects through the plate or disc I38 and is formed as indicated in Figure 6 to provide a driving connection with a pinion I48. One of these pinions I46, is of larger pitch diameter than the remainder for a reason by the plate I51 secure positive locking of the wheel I52 in the following manner:

' Assuming the ratchet parts to be in the position illustrated by Figure 8 of the drawings, then to bring the next successive stop I36 into position, the plate I51 is moved to the left as viewed in Figure 8, or upwardly as in Figure 6, by a bell crank I63 means to be described, which causes the pawl I54 to engage the ratchet tooth at position I53A, thereby turning the ratchet wheel I52 since the stop I62 will have moved out of interfering engagement with the tooth shown at position I53B. When .the plate completes its movement to the left the stop I6I engages in back of the tooth at position I53C, as shown by the dot-dash lines, and this together with a detent member I61, secured to the plate I46, holds the tooth at position I53C in a positive manner. As the plate I51 is returned toward the right under the influence of a spring I66 (Fig. 6), the pawl I54 (Fig. 8) rides over the top of the tooth I53, which has just been moved to the position I53A, holding the tooth now at pbsition I530 against the detent member I61 until stop member I62 is in place behind the tooth now at posi. tion I533.

The plate I51 is reciprocated in the manner just described to turn the shaft I 42 by the previously mentioned bell crank member I63 (Fig. 6) pivoted at I68, to a bracket I69 secured on the casing of the solenoid I30. One arm "I of the bell crank is pivotally connected at I12 to the ratchet plate I51 and the remaining arm I13 is provided with a member I14, preferably of brass or other non-magnetic material, which projects into the bore of the solenoid I38 so as to be engaged by the core I28 as it approaches I the end of its stroke.

A knob or handle 'membef I16, conveniently formed to be grasped and rotated, is secured upon a hollow rod or shaft I11, an end of which extends exteriorly of the casing or panel of the be described.

It will be apparent from the drawings taken with the foregoing description that the stops will be moved longitudinally between the limits defined by the plates I38 and I88 to position the stops for abutting engagement with the yoke I21 upon rotation of pinions I48 or the larger Pinion I48.

A step by step movement of rotation is imparted to the shaft I42 by a self-locking ratchet, details of which are best shown by Figures 8 and 9 of the drawings. Referring to these figures the ratchet mechanism I5I comprises a ratchet wheel I52, provided with teeth I53, there being one tooth, for each of the stops I36. A pawl I54 is connected at I56 to a plate I51, the latter being slidably mounted on a supporting web member I58 by means of a flange I60, which is struck outwardly to contact the edge of the plate. This web member may, for convenience, be attached to or form part of the previously mentioned mounting plate I46. The plate fits over the shaft I42 and is provided with an elongated aperture I56, which permits it to slide laterally to an extent necessary to allow radio receiver. The hollow rod I11 is rotatably journaled in suitable bearings which permit it to be moved longitudinally, and it carries on its end a crown gear I18. This gear is adapted to mesh with and drive the pinions I46, or the large pin- 1' ion I49. When the handle I16 is in the position illustrated in Figure 6 of the drawings, thegear I18 is in mesh with the large pinion I48, so

.that the stop I36 may be shifted from one limit of travel to the other to adjust the inductance of the coils throughout their range from one extreme value to the other. This provides for rapid manual tuning of the receiver by turning the knob I16.

An extended portion I8I of the shaft I42 is provided with a radially projecting pin I82, position for engagement with a member I83 projecting from the hollow shaft I11. As the shaft I42 is rotated so that the pinion I49 occupies the position illustrated by Figure 6 of the drawings, the pin I82 will engage the member I83, thus moving the crown gear I18 inwardly or upwardly as viewed in Figure 6 to a position for meshing I49, A spring 8 of the drawings, the crown gear I18 must be manually moved by drawing the knob I18 outwardly into position to mesh eflectively with the small pinions I48. When the shaft I42 and the assembly carrying the stops I38 approach the position occupied in Figure 6 of the drawings, the pin I82 will engage the member I83 and automatically cause the crown gear I18 to be moved inwardly so that it will not interfere with movement of the pinion I48 into position.

Energization of the solenoid I38 to select, by means 01' the stops I38, pre-set stations in succession is accomplished by a switch I85 (Fig. 11) the contact members oi which are operated by a rod member I88 projecting through a bore in the control shai't I11 in a manner to provide an exteriorly projecting push button portion I81. Figure 6 illustrates a modification ofthe switch I85 omitting the muting contact to be described in connection with Figure 11 of the drawings.

While the knob I18 and button I81 have been described as projecting exteriorly oi the casing or panel of the receiver in which the tuning and station selecting device is used, it will be understood that these or other control means which may be provided may be extended to any convenient point or may be connected to any suitable type of mechanism for extending the operating distance.

The switch I85 of Figure 11 comprises a mut ing contact I88, a control contact I88 for connection to the solenoid I38 and a grounded contact I8I. The remaining terminal of solenoid I88 is connected to a suitable power source I82, which in conventional practice may be the storage battery of an automobile having one of its terminals connected to ground as at I83. The

battery I82 may be employed to energize the circuits of the receiver I22 over a conductor I84. If desired, the conductor I84 may include a switch I85 so as to obtain operation the-control mechanism independently of the receiver.

The connection I88 from the solenoid to the battery may include the movable contact I 81 of a main switch and, also, an ignition, or other control switch I88 for the automobile, if desired.

The muting contact I88 is connected to one side of the voice coil I88 0! the receiver sound reproducer so that upon pressing the button I 81 the contact I88 will be grounded by the contact I 8I to silence the receiver. When suillcient pres-' sure is exerted upon the button I81 to overcome the resilient pressure of both contacts I88 and I8I so as to cause engagement 0! the latter with I88, the solenoid I38 will be energized, provided switches I81 and I88 are closed, to withdraw the yoke I21 and rotate the stop assembly to bring the next stop in succession into position ior engagement by the yoke. This action will occur upon each operation oi the button I 81 causing closure of contacts I88 and I8I. The stop assembly will be advanced one step for each complete operation of the button I81, thereby progressively tuning in all oi the pre-set stations. When the stop assembly reaches the position illustrated by Figure 6 or the drawings. the receiver may be manually tuned throughout its operating range by turning the knob I18.

when desired, a foot control may be provided as pointed out above by the addition of a switch 28I corresponding to the switch 84 of the above noted co-pending aplication. A connection from the terminal 01' the solenoid coil is made to the stationary contact 282 of the foot actuated control switch 28I which is mounted upon the floor board 283 of the automobile. The switch "I also has a movable member 284 connected to ground as at 288. The switch 28I has a muting contact 281 connected to one terminal of the voice coil I88 oi the reproducer. The muting contact 281 of the switch MI is positioned to be engaged by the movable member 284 prior to engagement between the movable member 284 and the control contact 282. Thus, initial movement of member 284 of the switch 28I short circuits the voice coil I 88 to mute the radio set. This muting system is similar to that disclosed in the McDonald application mentioned above.

A plurality of switches may be positioned in any of the passenger compartments of the car, or a plurality of controlling switches in parallel may be employed in the manner set forth in the co-pending application.

The several positions of the shaft I42, which are obtained by repeatedly operating the button I81, are indicated by a drum 2 (Fig. 6). This drum bears suitable indicia, such as the numerals Ito 8 indicated by reference character 2 I2 and the letter D", the latter indicating the manual or dial tuning position of the stop assembly.

A portion of the drum 2 is visible through an aperture 2 (Fig. 10) in the casing or panel 2I5 oi the receiver I22. As Figure 6 of the drawings shows the mechanism in the "dial or manual tuning position, Figure 10 indicates that the letter D is visible through the aperture 2I4.

The panel 2I8 oi the receiver is provided with a scale 2I8 graduated in kilocycles or other suitable units, as indicated by the scale divisions 2I1. A pointer 2I8 (Figure 6) operated from the yoke member I21 cooperates with the scale 2I8 and thereby serves to indicate the position of the cores I28 with respect to their respective inductances. To operate the pointer from the yoke a member 2I8 is secured on the yoke and has a pivotal connection at 22] to the pointer at a point between its ends. One end of the pointer is slotted as indicated at 222, the slot accommodating a stationary pin 224. Figure 6 illustrates the pointer at one end of the scale and as the yoke moves to the right the slotted end 222 oi the pointer will move inwardly over the pin 224, thereby flattening the path of travel of the indicating end oi? the pointer so that the scale 2I8 projects outwardly only a relatively small distance from the panel 2I5 of the receiver.

Figures 12 and 13 of the drawings disclose another modification oi the tuner control of this invention which provides a ready means for tuning a radio receiver to preset stations by manipulation of any type .01 multiple contact switch. The tuning control mechanism indicated by reference character 238 is or may be similar to the stop mechanisms already described in connection with the Figures 1 to 6 of the drawings. The receiver as before may be of any conventional type, such as is shown diagrammatically in Figure 1. It will be understood that the assembly 238 positions tuning members 231 which cooperate with tunable inductances in the manner oi Figures 1 or 6. These tuning members 23I are carried by a bar member indicated at 232, which is secured upon a rod 233 connected to a solenoid core 284, The rod 233 may have its forward end 238 bent to cooperate with a plurality of stops or abutments 238 of the assembly 238, adjustably carried by the turret member 231. A member 238 fixed to the end 235 of the rod 233 serves as an abutment for a spring 2 which cushions a bufier 24I' carried by the end oi. the rod.

The turret member 231 is secured upon a shaft 243 which also carries a ratchet wheel 244 engageable by a pawl 246 so as to rotate the shaft 243 one step for each operation of the pawl. The pawl 246 is pivoted to an arm 241, which swings about the shaft-2'43 and is pivotally slidably connected to one arm of a bell crank 248 having its other arm pivotally and slidably connected to a lever member 249 the latter being pivoted on a fixed bearing member 25I. The lever member 249 extends from the pivot point 25I and is slotted at 252 to accommodate a pin 253 secured upon the rod 233. The upper end of the lever 249 is preferably positioned so as to be visible and cooperates with a scale 254 having suitable graduations thereon.

A manually operable switch 256 shown as a simple multiple contact switch, has a series of stationary contacts 251 cooperating with a series of movable contacts 258 to successively break contact between the stationary contacts 251 and the movable contacts 258. The switch 256 is so arranged that when the switch knob 259 (Figure 13) is turned to one of the positions indicated by the indicia 26!, the movable contact 258 corresponding to that setting .01 the switch will-=be" opened, for example, by member 262 on the switch operator 259. The stationary contacts 251 are connected to a suitable power source such as the battery 263, the remaining terminal of this battery being connected by way of a switch 264 to one terminal of the solenoid 266. The remaining terminal or the solenoid 266 is connected to a rotary switch 261 shown as being operated mechanically from the shaft 243 by a pinion 268 and a gear 269 on the switch shaft 21I. The switch 261 comprises a rotary member 212 on the shaft 2" which is provided with oppositely disposed contacts 213 and 214. One or the other of these contacts moves over a set of stationary contacts 216, one of which is provided for each of the movable contacts 258 of the switch 256.

By reason of the gear reduction provided by gear 269 and pinion 288, contacts 213 or 214 move over the contacts 218.

In operation or the modification just described the manually operable switch member 259.(Figure 13), which serves as a tuning 'dial, is moved to any position at which a 'pre-set station will be received. For example, as shown in Figures 12 and 13 the turret operating mechanism 230 is in position corresponding to the position marked 4 on the switch 256, then when the switch handle 259 is moved to position 1 as shown in Figure 13 of the drawings the solenoid 266 will be energized by reason of engagement of contact 214 with the stationary contact 218 corresponding to closed contacts 258 and 251 at position No. 4 of the switch 256. This willcause energization of the solenoid to withdraw the member 233 to the left to the position shownmoving the cores 23I in a manner explained previously. This movement of the solenoid core 234 also compresses the spring 24I. Also, the switch 264 will be opened by an extension 211 on the core 234. The energy stored in the compression spring'24l will move the member 233 to the right rocking the lever 249 by reason of its connection at 252. This will move the pawl 246 by means of the bell crank 248, a distance of one tooth, thereby moving the turret 231 one step to place the next successive stop 236 in the path of movement of material.

the member 235. This operation will be repeated until contact 213 engages the contact 216 associated with the open contacts 258 and 251 corresponding to position 2 of the switch 259. That is to say the solenoid is energized, whenever the rod 233 is in its rightmost position and a circuit is completed through the switches 261 and 256, to move the rod 233 to the left. The switch 264 then breaks the solenoid circuit to permit the rod 233 to be returned to the right by the spring 24I and this operation is repeated until the position of the switch 261 corresponds to the position of switch 256. The stops 236 in the turret 231 are, it will be understood, provided with pinions 218 in the manner already described in connection with Figure 1 of the drawings. These pinions 218 cooperate with a gear 219 which is driven by a gear 28I. When the switch operator 259 is placed in the manual position indicated by the letter M the pinion 218 for the stop 236 corresponding to that position is brought into mesh with the gear 219. At other positions of the turret 231 means may be provided as disclosed in Figure 1 of the drawings to bring the gear 219 into mesh with the pinion 218 brought to a position adjacent to that gear to provide for pre-setting the stop to select a different station.

Figures 14 to 18 of the drawings disclose another modification of the tuner control mechanism of this invention. This modification, indicated generally by the reference character I5I', includes features of the mechanism 2! of Figure 1, and, therefore, the similarity existing between these embodiments of the invention will be pointed out as the description proceeds. The receiver I52, like the receiver of Figure 1 may be of any conventional type, but as illustrated in Figure 14, the tuning mechanism is designed for tuning an auto radio receiver, the compact outlines of which are shownin Figures 14 and 15 of the drawings. The receiver and tuning mechanism are enclosed by a casing I53. Figure 19 shows the electrical features of the mechanism I5! and also indicates diagrammatically the position of a foot operated switch I54, which is or may be similar to the foot control pedal 284 of Figure 11.

The plurality of tunable inductances in the form of coils I56, I51 and I58, corresponding in function to the inductances 6, 9 and I1 of Figure 1, are tunable by three cores I59 of low loss These cores are individually secured to a yoke member I6I' of sheet metal or other suitable light weight material by insulating members I62. As was pointed out in connection with Figures 6 to 11 of the drawings, circuit control or adjusting devices of many kinds may be connected to the yoke member I6I or its equivalent. Each member I62 is grooved as indicated at I63, so that it will be retained in an aperture in the yoke member I6I. Each core I59 is provided with a threaded stem I64, which is received in a nut I66 embedded in the member I62'.

The coils I56, I51 and I58 are wound on tubular members I61, each tubular member being held in position on a metallic shield I68 by an opening in an insulating bushing member I69 and a plug member I1 I The plug member I1I for the coil I56 serves to clamp the tubular member, the shield and a mounting plate I12 to a supporting bracket by .means of a screw I14 engaged in a threaded bore in the plug. The remaining two coil assemblies are secured directly to the plate I12 by their plugs HI and screws I14. Each coil is surrounded by a tubular member I16 of high permeability magnetic material which is positioned between the insulating bushing member I69 and a bushing I11 at the base of the shield.

The yoke member I6! is secured to the end of a solenoid core I18 by suitable fastening means I19 (Figure 15). A solenoid I8I, which slidably receives the core I18, comprises a magnetic frame I82 supported on a sheet metal platform or the like I83. A U-shaped member I84 of non-magnetic material is suitably secured to the magnetic frame I82 of the solenoid. The core I18 projects through an aperture in the non-magnetic member I84, providing a longitudinal space to accommodate a ratchet operating plate I86 and a sleeve-like hub I81 thereon. A buffer member in the form of a soft, resilient washer I88 is interposed between the yoke I6I and the member I84. A spring I89 serves to move the yoke I6I to the right, as viewed in Figure 14, and also performs the function of maintaining the yoke in a positiondetermined by one of a plurality of stops or abutments I98 and an additional stop or abutment I90a. The number of these stops may vary, depending on the number of positions of the yoke I6I or its equivalent, which are to be selected automatically.

Rotation of the yoke member I6 I is prevented by guide rods I9I secured to a member I92 carried by the previously mentioned support or shelf I83. One of the apertures I93 which receives the lower guide rod I9I may be elongated, as shown in Figure 15, to provide for slight errors in locating the rods I9I in the frame I92.

Each of the stops I90 is provided with an internally threaded aperture in which is received an externally threaded rod I94. The stop member mm is longitudinally moved by a rod I94a provided with threads of longer pitch than the rod I94. The stops are split as at I96 (Figure 15) to provide frictional clamping engagement with the threaded rods. The rods I94 and the rod I94a are rotatably supported in flanges I98 and I99 formed integrally with or secured upon a shaft 260. A hexagonal portion 28I of this shaft prevents rotation 'of the stops while permitting them to move longitudinally of the shaft. The shaft portion 20I' may be of any desired configuration in cross section designed to prevent rotation 01' the stops. The shaft 200 is supported in bearing members 292 and 263 suitably secured to the support I83. Each of the rods I94 projects through the flange I99 and has secured thereon a pinion 206. The rod [94a is provided in this manner with an enlarged pinion 206a for a purpose to be described later:

The bearing flanges I98 and I99 and the parts carried thereby constitute a turret assembly 281 which is rotated angularly one-sixth of a turn, in the embodiment of Figure 14, by a ratchet mechanism comprising a ratchet wheel 288 (Figures 14 and 16) having angularly spaced teeth 209. The angular spacing of the teeth 209 is equal to the angular spacing of the stops I90 on the turret assembly. Step by step movement is imparted to the wheel 208 by a pawl member H I (Figure 16) carried by the previously mentioned operating plate I88. Helical cam slots H2 in the hub I81 secured to the plate I86 receive a pin 2I4, which is secured to the sole noid core I18. The ratchet plate I86 is retained in the full line position of Figure 16 by means of a spring H6. The plate I86 is swung to its dotted line position by the pin 2I4 sliding in the cam slots 2I2. The tendency of the core I18 to rotate is prevented by the guide rods I9I The ratchet wheel 208 is held securely against accidental rotation by a member 2I1, engaged with the back of the ratchet tooth at the position 269a. The member 2I1 is mounted on the magnetic frame structure I82 of the solenoid. An upturned ear 2I9 on the plate I86, engaged in front of the tooth at the position 209a, prevents rotation of the ratchet wheel I08 in a forward direction. An additional stop for this purpose is provided by the upturned ear 22I which is engaged in front of another tooth adjacent the one at position 209a. The pawl 2II has a slightly inclined end 222 (Figure 16) which permits it to pass over the tooth at position 209?) as the plate approaches its dotted line position. The end 224' (Figure 14) of the slot 226' in the pawl will engage behind the tooth at position I992; as the plate returns to its full line position.

When the solenoid I8I is energized under the control of a switch in a manner to be described, the pin 2 I4 enters the cam slot 2I2 and rotates the plate I86 to its dotted line position in Figure 16. During this movement, the end 222 of the pawl 2II passes over the front of the ratchet tooth at position 2091) to engage the end 224 of the slot 226 behind the tooth. When the solenoid I8I is deenergized, the core I18 moves to the right as viewed in Figure 14 under the influence of the spring I89 and returns the plate I86 to its full line position, thereby advancing the turret assembly one step to bring the next successive stop I9I) into position to arrest the return movement of the yoke I6I The stops I90 and I9Ila are adjusted longitudinally of the turret assembly by a crown gear 221 secured on or integral with a hollow shaft 228.

This hollow shaft is provided at or adjacent its end with a knob member 229 and is journaled in bearing members HI and 232. The bearing member 23I is secured to an upstanding portion 233 of a plate member 234 (Figure 17). This supporting plate member is secured by suitable fastening means 296 to the supporting shelf I88. The bearing member 232 (Figures 14 and 17) is in the form of a disc which is retained in its initial dished shape by being confined at its circumference in a groove 281 provided by an annular recess in an annular member 298'. The annular member 288 is secured against an upturned portion 239 of the supporting member 234. The shaft 228 is retained in its bearing aperture in the disc 292 by means of a snap ring 24I' seated in a groove at the end of the shaft 228. The previously mentioned crown gear 221 is secured on the shaft 228 at a point such that it will be in mesh with the pinion 286a when the turret assembly is in the position shown by Figure 14. With the turret in any other position, the gear 221 may be brought into mesh with a pinion 206 by grasping the knob and pulling it outwardly to the position indicated by the dotted lines of Figure v17. The shaft and gear are maintained in this position by the snap action of the disc 232. The disc 282 maintains the shaft 228 firmly in either position without interfering with its freedom of rotation. With the knob 229 in its dotted line position, any one of the stops I96 may be moved longitudinally by turning the knob 229'. Operation of the ratchet mechanism by the solenoid I8I is prevented at this time since the operating circuit of the solenoid is opened at the switch contacts 242,

' one of which is engaged by the insulating sleeve 244 as shown by the dotted lines in Figure 17.

' previously mentioned Energization of the solenoid I8I' to select preset stations in succession is accomplished by the switch 246' (Figures 14, 17, and 19), the cohtact members of which are operated by a rod member 241 projecting through a bore in the pontrol shaft 228. A push button 248 is provided at the end of the rod 241. The rod and button are retained in position in the hollow shaft by a shoulder 249' on the knob 229. The knob 229' is concave as indicated by reference character 25I to assist in locating the button 248 by touch.

Figure 19 of the drawings illustrates diagrammatically the electric circuit connections of the solenoid and controlling switch 246. The switch 246, shown in greater detail in Figure 17, comprises a grounded contact spring member 253 secured to sheet 254' of insulating material, the latter being secured to the underside of the shelf I83 by suitable fastening means, such as the rivets 236'. The contact spring member 253 is provided with contacts 255 and 256 (Figure 14) which are adapted to engage, respectively, a muting contact 258 and a control contact 259. These last named contacts are carried by contact springs secured to the insulating plate 254, thereby to be insulated from the grounded parts of the tuning mechanism. The muting contact 258 is connected to one side of the voice coil of a sound reproducer 262' so that upon exerting moderate pressure on the button 248' the contact 255 will engage the contact 258' to short circuit the voice coil of the reproducer and silence the receiver. When sufficient pressure is exerted upon the button 248 to overcome the resilient action of the contact spring 243 and the spring supporting the contact 258, the contact 256 will engage the control contact 259'. A circuit is thereby completed to energize the solenoid I8I from the contacts 256 and 259, the switch 242, the conductor 266, the solenoid I8I, a receiver power switch 261, and a power source shown as the battery 268. Upon completion of the circuit just described the yoke member IBI' will be drawn to the left as viewed in Figure 14 against the tension of the spring I89. The pin ZI I will enter the cam slots 2I2' duringmovement of ground at 264',

be pushed inwardly to disengage the crown gear 221' from the pinion 206, the snap disc 232 again assuming its initial configuration. Inadvertent operation of the tuning mechanism at any time during the setting of a stop I90 by operating the switches 246 or 269 is prevented by reason of the contacts of the switch 242 being retained in circuit opening position by the insulating sleeve 244 when the shaft 228' is in the dotted line position indicated on Figure 17.

The parts including the hollow shaft 228 and the contact operating rod 261 may be proporthe solenoid core to thereby rotate the ratchet plate I86 to bring the pawl 2| I into operative engagement with a tooth on the ratchet wheel 208 in the manner described above. When the button 248' is released, the solenoid core will be moved or returned to the right by the spring I89, causing the ratchet pawl 2| I to rotate the turret to bring the next successive stop I90 into position for engagement by the yoke I6 I to tune in a station automatically. The turret assembly will be advanced one step for each operation of the button 248, thereby progressively to tune in all of the preset stations.

When desired, any one of the stops I90 may be preset to position the yoke member IBI to tune ina given station by drawing the knob 229 outwardly, bringing the gear 221 into mesh with the pinion 206' associated with the stop selected for adjustment. The snap disc 232 snaps to its reversed concave shape and holds the gear 221 in mesh with the pinion 206 without, however, interfering with the freedom of rotation of the gear. The knob 229' may now be rotated to turn the threaded rod I94 associated with the stop I90 selected for adjustment until satisfactory reception of the desired station is obtained. When this is accomplished, the knob 229 may tioned so that the switch 246 is inoperative to close the contacts 25B and 259 when the shaft 228 is drawn outwardly: These parts may also be proportioned so that only the muting contact may be engaged when the hollow shaft is withdrawn to preset one of the stops. The muting contact (described below) of the foot switch I54 is preferably available at all times.

A connection is made from the terminal of the solenoid I8I to the stationary contact 210 of the foot switch I54 by way of the switch 242" and the conductors 266 and 212'. The switch I54 also has a muting contact 213 connected to the voice coil of the reproducer 262 by way of the conductor 274 to accomplish muting of the receiver by grounding contact 273 by the grounded movable contact 269. The switch I5 3 is operated in the samemanner as the switch 21H of Figure 11. her 259 silences the receiver and further movement thereof selects the next successive stop I to thereby select a preset station. This operation may be repeated to select the preset stations successively.

In certain installations it may be desired to ground the contact member 269 on a metallic portion of the tuning device I5I or its associated apparatus, for example, the receiver I52. To accomplish this and to provide for a convenient and readily detachable connection of the foot switch to the tuning apparatus I5I, a socket or receptacle 278 is secured in an aperture in the receiver casing I53 (Figures 14, 20 and 21) by suitable fastening means 280. The contact 28l of the receptacle 21B is connected to ground and is adapted to engage a contact prong 283 on the plug 284 which is connected to the metallic shell 286' of the plug and in turn to the metallic sheath 281 of the cable 288. The remaining contacts 289' and 29I of the receptacle 218 are connected to the conductors 212 and 214' (Figures 19 and 20) which connect to the switch 262 and the voice coil of the reproducer 262', respectively. An annulus 292', forming part of the receptacle 21B, is provided with annularly disposed spring fingers 293 which frictionally engage the metallic shell 286 which surrounds the body of the plug 284. The conductors within the cable 288' are .suitably connected to the contacts within the switch E54, and the cable sheath 281' is or may be connected to the body or casing of the switch I54 which may in turn be connected to the contact 269. The indicator drum 299, similar to the drum I3I of Figure 2 of the drawings, is provided to indicate the several positions of the shaft 200. The drum 299 bears numerals l to 5 indicated by the reference character 300' and the letter D to indicate the manual or tuning position with the stop IBM in engagement Initial movement of the memface of the casing I53 to cooperate with a pointer 303'. The pointer 303' is pivotally connected to a bracket member 304' (Figure which is secured to the yoke I6 I by suitable fastening means as the screw 306'. Displacement of the bracket is prevented by a tang 301' which is engaged in an aperture in the yoke IN. The end of the pointer 303 is provided with a slot 308 (Figure 14) to engage a pin 309' secured to a stationary portion of the mechanism. When the cores 159 are fully inserted in their corresponding inductances, the pointer 303' is at one end of the scale to indicate that the receiver is tuned to one extreme end of its range.

It will be seen from the foregoing description that control apparatus embodying the present invention is capable of use in a wide variety of control equipment and may be readily and cheaply constructed without resorting to delicate and costly machine work in the manufacture of the parts. Accurate fitting operations during assembly of the parts constituting a control device embodying this invention are not necessary. Radio apparatus embodying the present invention is convenient to use and may be compactly constructed. It is capable of being accurately tuned by the simple operation 01' pressing a button, manipulating a simple switch or operating a. foot pedal. This feature or compactness permits radio apparatus embodying the present invention to be installed in vehicles, boats, and aircraft. The tuning and control system of the present invention is particularly applicable to the control of automobile radio sets and has been described in detail with respect to operation from low voltage batteries. However, other types of radio sets, such assets operated from alternating currenbor higher voltage direct current may be operated at the set or from a remote point in accordance with the principles of the present invention.

While the invention has been described and explained in detail in connection with several illustrative embodiments thereof, it is to be unstops with said member in a predetermined order, switch means, an electrical circuit including said switch means for energizing said electromagnet whereby to move said member upon operation of said switch means, and means for operating said switch means to effect control of said equipment.

2. Apparatus for the control of electrical equipment comprising a movable controlling member, an electromagnet for moving said member in one direction, resilient means tending to move said member in the opposite direction, a movable stop assembly comprising spaced stops, means operably connected to said electromagnet to move said stop assembly successively to position said stops for cooperation with said movable mem-- ber, switch means, an electrical circuit including said switch means for energizing said electromagnet whereby to move said member upon operation of said switch means, and means for operating said switch means for energizing said electromagnet.

3. In apparatus for the control of electrical equipment, movable means for effecting control of said equipment upon movement from one extreme end of its range of movement to thezother, power means for moving said movable means in one direction throughout its range of movement, a movable abutment in the return path of said movable means, and means for returning said movable means toward said abutment.

4. In apparatus for the control of electrical equipment, a movable controlling member, power means for moving said member in one direction, resilient means tending to move said member in the opposite direction, a rotatable stop assembly comprising angularly spaced stops, means operably connected to said power means to rotate said stop assembly and thereby successively to position said stops for engagement with said member, and means for controlling the operation of said power means.

5. In a system for controlling electrical apparatus, a movable control device, means for positioning said control device in a plurality of apparatus controlling positions, said means comprising a plurality of adjustable abutments for cooperation with said movable control device to position the same, electrical means for effecting simultaneous movement of said control device and selecting one of said abutments for cooperation with said control device, andmeans for adjusting the cooperating position of the one of said abutments selected for cooperation with said control, device while engaged with said control device.

6. Apparatus for the control of electrical equipment comprising a movable control device, an electromagnet for moving said control device in one direction, means tending to move said control device in the opposite direction, a movable stop assembly comprising stops designed to arrest movement of said control device when moving under the influence of said first named means, means operablyconnected to said electromagnet to move said stop assembly, switch means, an electrical circuit including said switch means and said electromagnet for energizing said electromagnet whereby to move said control device, means for adjusting the abutting position of said stops on said stop assembly, and manually operable means designed for cooperation with said stop adjusting means.

7. Apparatus for the control of electrical equipment comprising a movable control device, an electromagnet for moving said control device in one direction, means tending to move said control device in the opposite direction, a rotatable stop assembly comprising preset stops designed to arrest movement of said control device when moving under the influence of said first named means, means operably connected to said electromagnet to rotate said stop assembly to successively position said stops for cooperation with said control device, switch means comprising a movable member capable of partial or full actuation, an electrical circuit adapted to cause control of said electrical equipment upon partial actuation of said switch member, and an additional electrical circuit including said switch means and said electromagnet for energizing said electromagnet whereby to move said control device upon full actuation of said clutch member.

8. In a control device, a plurality of stop members, each member having a threaded aperture, a plurality of threaded members one for each stop extending through said apertures, spaced supporting members supporting said threaded members adjacent their ends, a shaft carrying said spaced supporting members, and means on said shaft for engagement with said stop members to prevent rotation thereof when said threaded members are rotated to adjust the position of said stop members.

9. A tuner for a radio receiver comprising a movable tuning device, an electromagnet for moving said tuning device in one direction, resilient means tending to move said device in the opposite direction, a stop assembly comprising spaced stops, means on said tuning device for engaging with said 'stop assembly, means to bring about engagement of said stops with said tuning device in a predetermined order, switch means, and an electrical circuit including said switch means and said electromagnet for energizing said electromagnet whereby to move said tuning device upon operation of said switch means.

10. A tuner for a radio receiver comprising a movable tuning device, an electromagnet for moving said tuning device in one direction, resilient means tending to move said device in the opposite direction, a movable stop assembly comprising spaced stops, means operably connected to said electromagnet to move said stop assembly successively to position said stops for cooperation with said tuning device, switch means, an electrical circuit including said switch means for energizing said electromagnet whereby to move said tuning device upon operation of said switch means, and means for operating said switch means fOr energizing sad electromagnet.

11. In a tuner for radio apparatus, longitudinally movable means for tuning said apparatus from one extreme end of its tuning range to the other, means for moving said tuning means throughout the tuning range of said apparatus comprising a movable abutment engageable with said movable tuning means, means to adjust the position of said abutment while in abutting engagement with said tuning means, means normally urging said tuning means against said abutment, and electrical means for disengaging said tuning means from said abutment.

12. A tuner for radio apparatus comprising means movable to adjust said tuner from one extreme end of the tuning range to the other, a plurality of adjustable abutments for said movable means, means for positioning said abutments successively in the path of movement of said movable tuning means to thereby provide a plurality of preset tuning positions, means individual to each of said abutments comprising a rotatable threaded member in threaded engagement with its associated abutment for adjusting the abutting position of said abutments, a pinion secured to each of said threaded members, and means shiftable for driving engagement with said pinion associated with the one of said abutments positioned to engage said tuning means.

13. The combination of claim 12 wherein one of said rotatable threaded members is threaded to move its associated abutment at an increased speed, whereby said associated abutment is available for rapidly moving said tuning means from one end of its range to the other to provide continuous dial tuning of said apparatus.

14. The combination of claim 12 wherein one of said rotatable members is provided with means for causing its associated abutment to traverse its range of movement at an increased speed whereby said associated abutment is available for rapidly moving said tuning means from one end of its range to the other to provide continuous rapid tuning of said apparatus.

15. In a tuner for radio apparatus, longitudinally movable means for tuning said apparatus from one extreme end of its range to the other, a plurality of adjustable means for positioning said tuning means at predetermined longitudinally spaced points within the tuning range of said apparatus, means for positioning said plurality of adjustable means successively for cooperation with said first named means, adjusting means individual to each of said adjustable means for adjusting them from one end of the tuning range to the other successively as said adjustable means are positioned successively, and means shiftable to engage the adjusting means when said adjusting means are brought successively into engagement with said tuning means.

16. A tuner for a radio receiver comprising a movable tuning device, an electromagnet for moving said tuning device in one direction, resilient means tending to move said device in the opposite direction, a rotatable stop assembly comprising angularly spaced stops, means operably connected to said electromagnet to rotate said stop assembly successively to position said stops for cooperation with said tuning device, switch means, an electrical circuit including said switch means for energizing said electromagnet whereby to move said tuning device upon operation of said switch means, and means for operating said switch means for energizing said electromagnet.

17. A tuner for a radio receiver comprising a movable tuning device, means tending to move said device in one direction, an electromagnet for moving said tuning device in the opposite direction, a movable stop assembly comprising spaced supporting members, stop members carried by said supporting members, and means operatively connected to said electromagnet to bring about cooperation of said stop members with said tuning device in a predetermined order.

18. A tuner for a radio receiver comprising a movable tuning device, an electromagnet for moving said tuning device in one direction, resilient means tending to move said device in the opposite direction, a movable stop assembly comprising angularly spaced stops, means successively to position said stops for cooperation with said tuning device, said last named means operating in timed relationship with said electromagnet, switch means, an electrical circuit including said switch means and said electromagnet for energizing said electromagnet whereby to move said tuning device upon operation oi! said switch means, and means comprising a manual control for operating said switch means.

19. A tuner for a radio receiver comprising a movable tuning device, means tending to move said device in one direction, an electromagnet for moving said tuning device in the opposite direction, a rotatable stop assembly comprising supporting members and angularly spaced stop members, and means operatively connected to said electromagnet to impart increments of angular movement to said stop assembly substantially equal to the angular spacing between said stop 

